Electrochemical decontamination of nuclear graphite in deep eutectic solvents

Over 100 power plants worldwide have used graphite as moderator and structural material, which will result in approximately 300,000 t of irradiated nuclear graphite waste requiring long-term management. This contains radionuclides such as 60Co, 14C, and 3H, among other radioactive contaminants. Electrochemical decontamination represents a regenerative route for treating this waste while preserving the graphite matrix. Here, electrochemical decontamination of graphite in a choline chloride–urea deep eutectic solvent (ChCl–U) is investigated. A cobalt-implanted graphite surrogate was used to establish an efficient treatment protocol. Alternating positive and negative potentials applied to the graphite surface over 10 cycles removed >95% of implanted cobalt in 30 min at 150 °C. Structural characterisation indicates slight expansion of the graphite c-axis and intercalation of chloride ions and choline-derived species within the lattice. A mechanism is proposed in which repeated intercalation and de-intercalation cycles induce lattice strain and surface exfoliation. Applying this protocol to irradiated graphite from UK Magnox reactors achieved up to 30% removal of 60Co without measurable mass loss; while 241Am, 133Ba, and 155Eu recorded maximum decontaminations approaching 60%. These mechanistic insights establish a low-temperature electrochemical separation route that selectively extracts radionuclides while preserving the graphite matrix, reducing reliance on harsh reagents and offering a viable pathway for waste volume reduction and graphite recycling via selective interfacial radionuclide separation.